This article is based on a review of recent scientific literature and provides an overview of; the benefits of cycling, the associated injury risks, and the capability of current cycling helmets to protect wearers against head and brain injury from sudden severe impacts, and repeated minor head knocks.

Whether it be for transportation, exercise or just for fun, the popularity of cycling is growing. A number of cities worldwide, including London, have benefitted from promoting and supporting cycling as low cost, efficient means of sustainable and clean transportation. A review paper by Rabl and de Nazelle (2012) explains the health benefits of burning fat by pedaling, rather than fuel by driving, valuing the health benefits of one person switching from driving to cycling at €1300/year. Cleaner air, less traffic congestion, fewer road traffic accidents and a lower cost of living have also been demonstrated in cycling friendly societies (Rojas-Rueda et al., 2011).

It not all good news though, as with any sporting participation there is risk of injury. The old adage that “there are two types of cyclists, those who’ve fallen off, and those that will” is backed up by US statistics that report around half a million cycling related injuries per year, including 800 deaths (US Center for Disease Control and Prevention). Amongst these, head injury account for a high proportion of the severe and fatal injuries. Kids are particularly susceptible to cycling injury with a Cochrane review (Macpherson & Spinks, 2008) estimating that 35-40% of childhood injuries and deaths are from bicycle related head trauma.

There is no doubt that cycling helmets significantly reduce the risk of head and brain injury with new research from New York showing that hospitalized cyclists had fewer head CT scans, had fewer skull fractures and lower severity and rates of brain injury than non-helmeted cyclists (Sethi et al., 2015). Those results are supported by McNally and Whitehead (2013) who, using computer simulation of a bicycle vs. car crash, found helmets reduced the likely severity of head injury and offered considerable protection against fatality. These studies make a compelling case for the compulsory use of cycling helmets, as it is in countries like Australia. However, others make an argument that the protective benefits of compulsory helmet use on individual cyclists might be balanced by the detrimental health and environmental effects of any associated drop in cycling participation (SWOV).

Whilst protection against severe traumatic brain injury is vitally important, the management of concussion has recently become a major focus of the injury prevention community. Although considered a mild injury that usually resolves with a period of rest, there is growing evidence that repeated concussive episodes can have long term effects on brain health and function. Although further research is required, diagnoses such as early onset dementia and chronic traumatic encephalopathy have been associated with athletes who’ve sustained multiple concussions (McCrory, 2013).

So wearing a helmet when cycling is a good idea, but do they protect against all impact types? Most modern cycling helmets are mostly constructed of a hard plastic shell filled with crushable foam, usually in the form of expandable polystyrene (EPS). The helmet.org website provides excellent explanations on the types materials used in cycling helmets (http://www.bhsi.org/liners.htm) but in short, EPS is a stiff foam that crumples on hard impact to slow, and dampen the effect of high impact forces. This means that whilst it has been shown that EPS helmets do a good job protecting against big impacts (McNally and Whitehead, 2013) and severe injury, they only do it once and then need to be replaced. Further, the American Academy of Pediatrics position statement on bicycle helmets (2001) states “Even in low-impact falls, the helmet may be damaged by the force delivered, rendering it less effective in subsequent impacts”. Therefore, if you or your children have bumped, cracked or dented your EPS helmet, either on the bike or in the garage, its protective properties are likely to have been compromised (helmet.org). Whilst “tuning” the density of EPS foam so it only crushes on relatively firm impact makes them useful for saving cyclists in big crashes, the ubiquitous hard shells that remain rigid with less severe impacts aren’t likely to protect against relatively minor, concussive type impacts.

From the evidence presented, it seems important that more (all!) cyclists should wear a helmet when riding. For that to occur without discouraging people from cycling helmets will need to look good (aesthetics in likely to be a key factor in adult and adolescent helmet use), be compact and affordable. Most importantly, future helmets should incorporate materials and design that protects against all levels of head impacts. Thereby, not only reducing the risk of severe injury and fatality, but also minimizing gradual onset brain injuries attributed to repeated minor head knocks.